Siftproof bag



June 24, 1941.

W.-N. BAKER 2,246,911

SIFTPROOF BAG Filed July 13, 1940 INVENTOR mm Nams 5A KER BY Q M W ATTORNEY stage of bottom folding;

secondtstage of bottom folding wherein Patented June 24, 1941 SIFIPROOF BAG Webster Noyes Baker, Baldwin, N. Y., assignor to Bagpak, Inc., New York, N. Y., a corporation of Delaware Application July 13, 1940, Serial No. 345,318

6- Claims.

This invention relates to new and useful improvements in packaging containers and particularly seeks to provide a bag of rectangular crosssection, capable of standing squarely on its bottom and having its bottom walls so arranged as to be siftproof and air-tight.

Heretofore many forms of bags have been devised which tend to minimize sifting of pulverulent or powdered material through the bottoms thereof. However, such bags are formed in such a manner that one or more lines of fold, or even actual apertures, extending in more or less open communication with the interior of the bag are present and through which material can sift. Another difficulty heretofore encountered in the formation of. sift-proof bags has been the inability to provide a continuous adhesive bar so disposed as to effectively seal together all of the mutually contacting surfaces of the bottom folds.

The objectionable features above referred to are completely eliminated through the use of bags constructed in accordance with this invention.

Therefore an object of this invention is to provide a bag of rectangular cross-section which is capable of standing squarely on its bottom and having its bottom walls so arranged that there are no apertures or ducts formed by lines of fold which extend into open communication with the interior of the bag.

Another object of the invention is to provide a bag of the character stated that is formed from a multiply tube blank.

Another object of the invention is to provide a bag of the character stated in which only the outer ply of the blank is slit during the formation of the bottom thereof, thereby facilitating theformation of a sift-proof bottom..

Another object of the invention is to provide a bag of the character stated in which adhesive is applied to the bottom panel portions in such a manner as to effectively seal all ducts or apertures formed during the folding operations and to seal together the mutually contacting surfaces of the bottom to thereby assure a siftprooi bag.

These and other objects of this invention will become more readily apparent from the following description and with reference to the accompanying drawing in which Fig. 1 is a perspective view of a'tube blank before the bottom is folded;

Fig. 2 is a diagrammatic view showing the first Fig. 3 is a view similar to Fig.2 showing the the said walls of the tube have been folded into position to form a sift-proof bottom;

Fig. 4 is a plan view showing the manner in which adhesive is applied to the folded-bottom; an

Fig. 5 is a view similar to Figs. 2 and 3 showin the completely folded bottom.

Referring to the drawing in detail, the invention as illustrated is embodied in a paper bag formed from a duplex or multiply tube 5. The

tube 5 is preferably formed from an outer tube 6 and an inner tube 1 and is provided with gussets 8. It should be noted that the tube 5 is preferably so formed that the longitudinal seams of the inner and outer component tubes thereof are disposed in offset relation to assure a stronger tion of the bottom the inner tube 1 will be free of all cuts, thereby permitting the formation of a sift-proof bottom, As is customary in the formation of an automatically opening bottom, the tube 5 is provided with crease lines' [3 and I on which the tube is folded, as illustrated in Fig. 2 of the drawing, as the first operation in forming the bottom. The inner and outer plies are preferably secured together within the bottom forming area of the. tube by means of triangularly shaped pasted sections l5. The flap I2 is provided with a projecting portion or tongue I20 which is held by the gripper of the bottom forming mechanism. The opposite flap I0 is held as is well known in the art by means of pins which serve to assist in pulling the flaps Ill and I2 apart so that in the initial stages of 'the bottom formation, the end of the tube will be forced into the position shown in Fig. 2.

After the flaps have been pulled apart by the bottom forming mechanism the sidewall I6 is folded in a plane normal to the longitudinal direction of the bag tube. The opposite sidewall I1 is then folded in a like manner so that its marginal edge will overlap the marginal edge of a reentrant fold, the reentrant portion being-covered by the sidewall I1. In this manner any tendency towards sifting of the packaged material would result in such a movement of the material as to require it to follow a labyrinth of such nature that actual sitting of said material .will be virtually impossible. Reference to Fig. 4 of the drawing will disclose that the reentrant folds formed by an overlapping'of the,

sidewalls l6 and II are effectively covered by paste and totally dam the labyrinth formed by the folds.

After the sidewalls of the bottom have been folded into an overlapped relation a bar of adhesive 20 is applied to the exposed faces of the,

ing of any material which might work in between certain of the overlapped portions. After the adhesive has been applied the flaps l and I! are folded along crease lines 22 and 23, the flap l0 being folded into position prior to the folding of the flap l2. In order to effectively seal any ducts formed as a result of the folds of the creased lines 22 and 23, triangular sections 2| of adhesive may be included on each side of the adhesive bar 20. In forming the flaps Ill and I2, the slits defining the flaps III are spaced more closely than the slits defining the flap l2 so that the flap I2 effectively covers the flap l0 when the bottom is completely formed. In this manner sifting of mlaterial between the flaps l0 and I2 is effectively avoided. Thus it will be observed that the herein disclosed invention provides a sift-proof bag of rectangular cross-section which is capable of standing squarely on its bottom and having its bottom walls so arranged that there are no apertures or ducts formed by lines of fold which extend into open communication with the interior of the bag; in which only the outer ply-'of' the blank is slit during the formation of the directed triangular apices from the adjacent portions of said inner ply and characterized by reentrant folds covered by the edge of said overlapping wall portion' and located within the area defined by said flaps; thenapplying adhesive to portions of the plane surface thus formed; and finally folding one of said flaps over onto said plane surface and then folding the other flap over onto said first flap. 7

2. The method of forming a square bottom sift-proof bag from a gusseted multi-ply tubular blank consisting in slitting the ungusseted wall bottom; and in which adhesive is applied to the bottom panel portions in such a manner as to seal together the mutually contacting surfaces of the bottom.

It is of course to be understood that various modifications of the structure disclosed herein may be resorted to without departing from the spirit or scope of the appended claims.

I claim:

1. The method of forming a square bottom sift-proof bag from a multi-ply tubular .blank consisting in slitting two opposed wall portions of the outer ply of said blank to form resultant flaps; creasing said blank along lines extending transversely vof the walls containing said flaps preparatory to folding the bottom; folding one of the unslit wall portions of said blank inwardly; then folding the remaining unslit' wall portion inwardly, the edge thereof overlapping the edge of said first folded unslit wall portion, said folding steps thereby resultingin the formation of a substantially continuous plane surface and resultingin the projection of said flaps in opposite directions and the formation of outwardly portions of the outer ply of said blank to form resultant flaps; creasing said blank along lines.

extending transversely of the walls containing said fi'aps preparatory to folding the bottom; folding one of the gusseted wall portions of said blank inwardly; then folding the remaining gusseted wall portion inwardly; the edge thereof overlapping the edge of said first folded gusseted wall portion; said folding steps thereby resulting in the formation of a substantially continuous plane surface and resulting in the projection of said flaps in opposite directions, and a formation of outwardly directed triangular apices from the adjacent portions of said inner ply and characterized by reentrant folds covered by the edge of said overlapping wall portion and located .within the area defined by said flaps, then applying adhesive withinlimits defined by said flaps to portions of the plane surface thus formed and finally folding one of said flaps over onto said plane surface and then folding the other flap over onto said. first flap. e

3. In a process of manufacturing a sift-proof bag from a multi-ply tubular blank, the step of forming oppositely directed triangular apices characterized by reentrant folds from the inner ply thereof so disposed as to be covered by flap portions of the outer ply thereof.

4. In a process-of manufacturing a sift-proo bag from a multi-ply tubular blank, the steps of slitting two opposed wall portions of only the outer ply of said blank to form resultant flaps, and folding the bottoin to provide a pair of inangular apices formed from the inner ply of said blank and characterized by reentrant folds and located in such position as to be completely covered by said flaps.

5. A sift-proof bag formed from a multi-ply tubular blank and having a folded bottom including overlapping flap portions formed by slitting two opposed walls of only the outer ply of said blank, and triangular apices formed from the unslit inner ply of said blank, and underlying the respective flap portions and being wholly covered thereby, said apices being characterized by reentrant folds and covered by overlapping edge .portions of the outer ply of said blank.

6. A sift-proof automatic bag formed from a multi-p y gusseted tubular blank and having a .folded bottom including overlapping flap portions formed by slitting the ungusseted walls of only,

' the outer 'ply of said blank, and triangular apices beingwholly covered thereby, said apices being characterized by reentrant folds and covered by gilerlapping edge portions of the outer ply of said ank.

' WEBSTER. NOYES BAKER. 

